Method and means for controlling agitation of the contents of a crucible member of an induction furnace



Aprll 12, 1955 J. P. ROHN 2,706,212

METHOD AND MEANS FUR CONTROLLING AGITATION, OF THE CONTENTS OF ACRUCIBLE MEMBER OF AN INDUCTION FURNACE Filed Feb. 18, 1954 FIE. 3

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Tor-mm PETER ROHII United States Patent METHOD AND NIEANS FORCONTROLLING AGI- TATION OF THE CONTENTS OF A CRUCIBLE MEMBER OF ANINDUCTION FURNACE Johann Peter Rohn, Koln-Buchforst, Germany, assignorto Firma Russ-Elektroofen K. G. Koln, Koln-Bayenthal, GermanyApplication February 18, 1954, Serial No. 411,216

Claims priority, application Germany February 20, 1953 11 Claims. (Cl.13-27) This invention relates to an improved induction furnace and moreparticularly to an improved grooveless induction furnace operable onnormal power frequencies.

Grooveless induction furnaces operable on normal, power frequencies areknown in the prior art. Crucibles for such furnaces are normally made ofsteel or ceramic material. This type of furnace has not been used in thepast to any great extent because the forces generated by the inductioncoil or coils often cause such great agitation of the molten fluidwithin the crucible that this fluid is caused to rise over the rim ofthe crucible and splatter outside of the crucible.

In order to avoid the above difliculty, prior art furnaces have beenconstructed with three induction coils energized by three phase current.Different of the phases are interrupted in a random or arbitrary mannerso that at any given time only one or two of the coils are energized andin succeeding periods of time different ones of the coils are energized.In other arrangements employing a plurality of coils, the coils areenergized in some regular order by various switching arrangements,rheostats, etc.

The above methods have several disadvantages. One is that the life spanof the oven lining is seriously impaired because of the rapid, transientchanges in flux density. Furthermore, the prior art methods require, inorder to switch energy from one coil to another, various tappedtransformer arrangements, chokes, rheostats and other cumbersome andexpensive auxiliary control devices.

It is an object of the present invention to provide an induction ovenoperable on normal power frequencies such as 50 or 60 cycles which hasnone of the foregoing disadvantages.

In accordance with the invention there is provided an induction furnacewhich mainly consists of the combination of a crucible member and a coilmember disposed about the crucible member for heating the contentsthereof. Supporting means are provided for the crucible member and thecoil member, one of said supporting means being movable with respect tothe other of said supporting means. When one of said supporting means ismoved relative to the other, the agitation produced in the contents ofthe crucible is controlled and the contents are prevented fromoverflowing the crucible.

In one preferred embodiment of the invention, the crucible is mounted ona fixed base and the coil together with its iron core which surroundsthe crucible is moved up and down relative to the crucible. I

In a second preferred embodiment of the invention the crucible ismounted on a movable support and the coil and its core mounted on afixed support. A drive mechanism is provided for moving the crucible inaxial direction relative to the coil and its core.

In a third preferred embodiment of the invention the crucible and thecore are mounted on a fixed base and the coil which energizes the coreis driven by a drive mechanism.

In a final embodiment of the invention, the coil is movable relative toboth the crucible and the core from a position in which the coil isentirely retracted between the core assembly and the crucible to asecond position wherein the coil is at least partially outside of thecore.

The novel features which are considered as characteristic for theinvention are set forth in particular in the appended claims. Theinvention itself, however, both as to its construction and its method ofoperation, together with additional objects and advantages thereof, willbe best understood from the following description of specificembodiments when read in connection with the accompanying drawings, inwhich:

Fig. 1 is a cross-sectional view of an induction furnace in accordancewith one embodiment of the invention;

Fig. 2 is a cross-sectional view of an induction furnace in accordancewith another embodiment of the invention;

Fig. 3 is a cross-sectional view of an induction furnace in accordancewith a third embodiment of the invention; and

Fig. 4 is a cross-sectional view of an induction furnace in accordancewith a fourth embodiment of the invention.

In the various figures, like numerals refer to like elements.

Referring now to Fig. 1, there is shown a crucible 11 mounted on a base14 and surrounded by a coil 12 and magnetic core 13. The core and coilare slidably supported on the crucible by means of a movable supportingarm 16. This supporting arm is movable in the directions indicated bythe arrows by means of a drive mechanism 15 Fig. 2 shows a crucible 11and a magnetic core 21, both the core and crucible being supported on afixed base 22. The core is provided with a pair of apertures at thebotom end thereof through which a movable supporting structure 24passes. Coil 12 surrounds the crucible and is movable in the directionsindicated by the arrows by means of drive mechanism 23 which is coupledto the coil by the movable support 24.

In the embodiment illustrated in Fig. 3, coil 12 and magnetic core 13are mounted on a fixed base 20. Crucible 11 is mounted on movablesupport 17 which is driven in the directions indicated by the arrows bymeans of drive mechanism 19 and mechanical connection 18.

A fourth embodiment of the invention is illustrated in Fig. 4. In thisembodiment, the magnetic core 25 has an open portion at the bottom endthereof through which the coil 12 fits. The magnetic core and crucibleare mounted on a fixed base and coil 12 is mounted on a movable support28. The coil is driven by means of drive mechanism 27 from a firstposition in which the coil is entirely retracted within the magneticcore to a second position in which the coil is outside of the magneticcore.

In the operation of the invention illustrated in Figs. 1-4, relativemovement is caused between the crucible and the coil in the mannerindicated in order to control the operation of the furnace. Suchmovement is usually periodic and between two limits, however, theinvention is also applicable to aperiodic movement. Because of therelative movement of the parts, the agitation of the molten fluid withinthe crucible is kept within acceptable limits and the fluid is preventedfrom overflowing the crucible. In the embodiment illustrated in Fig. 4the furnace may, in effect, be shut off by causing the coil 12 to moveentirely or almost entirely outside of the magnetic core so that theheat induced is at a minimum. Similarly, in Fig. 3 the same effect maybe achieved by moving the crucible outside of the core and coil.

In the above-described embodiments, no details are given for the drivemechanism since such mechanisms are well known. The dashed lines 16, 18,24 and 28 may, for example, merely comprise a shaft. The shaft may bedriven by means of a piston cylinder arrangement which may be powered bya motor or which may even I be driven by a hand crank. Many other typesof drive mechanisms are equally applicable to the invention.

The various base members are usually constructed of some sort of heatinsulating material so that no heat is conducted away from the crucible.The illustration,

- of course, is merely schematic since almost any shape of base memberwould do provided a drive mechanism could be conveniently connected toeither the crucible or coil.

The various magnetic cores are made of iron laminations in the usualmanner.

Although no power source is illustrated, it is to be understood that thecoils are energized by normal alternating current at a frequency such as50 or 60 cycles. It is also to be understood that although a single coilis illustrated, it may be preferable in some cases to use two or morecoils and these coils may be driven either in synchronism orindependently.

The crucible illustrated in the various figures may be made from steelor ceramic material.

It will be understood that each of the elements described above, or twoor more together, may also find a useful application in other types ofinduction furnaces differing from the types described above.

While the invention has been illustratedand described as embodied in aninduction furnace operable at normal power frequencies, it is notintended to be limited to the details shown, since various modificationsand structural changes may be made without departing in any way from thespirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can by applying current knowledgereadily adapt it for various applications without omitting featuresthat, from the standpoint of prior art, fairly constitute essentialcharacteristics of the generic or specific aspects of this inventionand, therefore, such adaptations should and are intended to becomprehended within the meaning and range of equivalence of thefollowing claims.

What is claimed as new and desired to be secured by Letters Patent is:

1. An induction furnace, comprising, in combination, a crucible member;an induction coil member surrounding said crucible member for heatingthe contents of said crucible member; and drive means coupled to saidcoil member for moving it relative to said crucible member, whereby theagitation produced in the contents of said crucible member due to theinductive heating thereof is controlled and said contents are preventedfrom overflowing said crucible member.

2. An induction furnace, comprising, in combination, a crucible member;an induction coil member surrounding said crucible member for heatingthe contents of said crucible member; and drive means coupled to saidcrucible member for moving it relative to said coil member, whereby theagitation produced in the contents of said crucible member due to theinductive heating thereof is controlled and said contents are preventedfrom overflowing said crucible member.

3. An induction furnace, comprising, in combination, a fixed support anda movable support; a crucible member mounted on said fixed support; aninduction member comprising a coil surrounding said crucible member, anda magnetic core for said coil coaxial about said coil, said inductionmember being secured to said movable support and being slidably mountedon said crucible member; and a drive mechanism connected to said movablesupport for moving said induction member in axial direction relative tosaid crucible member, whereby the agitation produced in the contents ofsaid crucible member due to the inductive heating thereof is controlledand said contents are prevented from overflowing said crucible mem- 4.An induction furnace, comprising, in combination, a crucible membermounted on a fixed support; an induction member comprising a magneticcore surrounding said crucible member and mounted on said fixed support,there being a space between said magnetic core and said crucible member,and a coil surrounding said crucible member and located in said spacebetween said crucible member and said magnetic core, said coil being inslidable engagement with said crucible member and being movable in axialdirection; and a drive mechanism connected to said coil for moving thesame in axial direction relative to said crucible member and saidmagnetic core, whereby the agitation produced in the contents of saidcrucible member due to the inductive heating thereof is controlled andsaid contents are prevented from overflowing said crucible member.

5. An induction furnace comprising, in combination, an induction memberincluding a coil and a magnetic core coaxial with said coil, saidinduction member being mounted on a base member; a movable supportingmember; a crucible member located within said induction member andsupported by said movable supporting mem her; and a drive mechanismconnected to said movable supporting member for moving said cruciblemember in axial direction relative to said induction member, whereby theagitation produced in the contents of said crucible member due to theinductive heating thereof is controlled and said contents are preventedfrom overflowing said crucible member.

6. An induction furnace comprising, in combination, a crucible membermounted on a fixed support; a magnetic core mounted on said fixedsupport and surrounding said crucible member, there being a spacebetween said crucible member and said magnetic core; a coil surroundingsaid crucible member and located in the space between said cruciblemember and said magnetic core, said coil being in slidable engagementwith said crucible member and being movable in axial direction from afirst position in which said coil surrounds a portion of said cruciblemember to a second position in which the coil is moved entirely outsideof the space between said magnetic core and said crucible member; anddrive means connected to said coil for moving it between said first andsecond positions, whereby the agitation produced in the contents of saidcrucible member due to the inductive heating thereof is controlled andsaid contents are prevented from overflowing said crucible member.

7. An induction furnace comprising, in combination an induction memberincluding a coil and a magnetic core coaxial with said coil, saidinduction member being mounted on a base member; a movable supportingmember; a crucible member located within said induction member andsupported by said movable supporting member; and a drive mechanismconnected to said movable supporting member for moving said cruciblemember in a periodic manner in axial direction relative to saidinduction member, whereby the agitation produced in the contents of saidcrucible member due to the inductive heating thereof is controlled andsaid contents are prevented from overflowing said crucible member.

8. An induction furnace, comprising, in combination, a crucible member;an induction coil member surrounding said crucible member for heatingthe contents of said crucible member; supporting means for supportingsaid crucible member; supporting means for supporting said coil member,at least one of said supporting means being movable relative to theother of said supporting means; and drive means connected to the movableone of said supporting means for moving it in a periodic manner relativeto the other of said supporting means.

9. An induction furnace, comprising, in combination, a crucible member;an induction coil member surrounding said crucible member for heatingthe contents of said crucible member; supporting means for supportingsaid crucible member; supporting means for supporting said coil member,at least one of said supporting means being movab e relative to theother of said supporting means; and drive means connected to the movableone of said supporting means for moving it in a periodic manner betweentwo limits relative to the other of said supporting means.

10. In an induction furnace having a crucible member and an inductioncoil member surrounding said crucible member for heating the contents ofsaid crucible member, a method for controlling the agitation produced insaid contents comprising the step of moving one of said members relativeto the other of said members in a periodic manner.

11. In an induction furnace having a crucible member and an inductioncoil member surrounding said crucible member for heating the contents ofsaid crucible member, a method for controlling the agitation produced insaid contents comprising the step of moving one of said members relativeto the other of said members in a periodic manner between two positions,one in which the induction coil member surrounds the to portion of saidcrucible member, and the other in which the induction coil membersurrounds the bottom portion of said crucible member.

References Cited in the file of this patent UNITED STATES PATENTS1,144.034 Giolitti June 22, 1915 1,879,360 Linnholf Sept. 27, 19322,665,320 Chadsey, Jr. et a1 Jan. 5, 1954

